[Sidefx-houdini-list] Linear workflow

François Duchesneau sidefx at trinix.ca
Thu Mar 3 18:56:00 EST 2016


Great. Thanks for the detailed info. I underestimated the complexity of 
color space I think.

And thanks Edward too. I'll pass this info to see if they can implement 
a lut that matches more closely the one we have in Nuke.

Cheers

Francois

On 03/03/2016 07:57 AM, Matt Estela wrote:
> You haven't provided enough information to say definitively 'yes' or 'no'.
>
> A 3d lut can be baked down to a 1D lut that mplay can use, again Aces
> provides tools to do this (there might even be a lut baker that ships with
> houdini, its been a while since I looked).
>
> Anyway, it sounds like you're not going to get much help from your
> co-workers or the client, so the only thing you can do is test. Get the
> compers to write you out a linear exr of something, that they can load back
> into nuke, view through the lut, confirm it looks as expected.
>
> Take that into houdini, make a shader that loads the exr and feeds it
> directly to Cf. Assign that shader to a plane, render out an exr, view that
> in nuke. Ideally, it should look identical to the original image. If you
> can get a 1D lut baked for you, it should look identical in the render view
> and mplay too.
>
> If that all checks out, then try more ambitious tests of overexposed and
> underexposed images, run them out of nuke, into houdini, back to nuke, you
> shouldn't see any change.
>
> If you can't get a lut to use in houdini, then you'll have to just struggle
> as best you can by adjusting the colour correction values in the render
> view so that they match as close as possible to the nuke lut. Beyond that,
> you'll have to just accept you're working in a non-look-lut space, and
> frequently write out exrs to load in nuke to confirm you're staying on
> track.
>
>
>
>
>
> On 3 March 2016 at 10:24, François Duchesneau <sidefx at trinix.ca> wrote:
>
>> And then based on this new information I added, would the answer still be
>> yes?
>>
>> Thanks again guys
>>
>> Francois
>>
>>
>> On 03/02/2016 09:01 AM, François Duchesneau wrote:
>>
>>> I don't think this lut is for a particular monitor color space because we
>>> use it only for a certain project. Actually, some shots within the projects
>>> don't use any LUT and we look at our renders with 2.2 gamma in mPlay.
>>>
>>> It is a 3D LUT provided by the client used to visualize their plates that
>>> behaves similar to the second case you described. They advised me to make a
>>> color correction in Nuke per channel on the HDRI to make things look right
>>> when I light.
>>>
>>> In fact yesterday somebody told me Houdini doesn't allow 3D LUT so what
>>> we're looking in mPlay is not even right.
>>>
>>> Francois
>>>
>>> On 03/02/2016 02:02 AM, Matt Estela wrote:
>>>
>>>> Depends. :)
>>>>
>>>> If the lut you're using has taken linear into consideration, (eg, you're
>>>> using an aces colour pipeline, and the person in charge has made you a
>>>> lut
>>>> for mplay that does scene linear -> monitor conversion), yes.
>>>>
>>>> If it's some random lut created by the DOP/grading department to make the
>>>> highlights vaguely green, mids a delicious purple and crush the blacks a
>>>> little (ie, its a look LUT), the answer is probably no.
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